Cam arrangement for programming system



Nov. 10,1970 J. LOCKARD ETAL 3,53,?

CAM ARRANGEMENT FOR PROGRAMMING SYSTEM Filed Nov. 29, 1968 INVENTOR.

rrosw LARUE LOC KARI) WILLlA HENRY ROSE United States Patent C W 3,539,970 CAM ARRANGEMENT FOR PROGRAMMING SYSTEM Joseph La Rue Lockard and William Henry Rose, Harrisburg, Pa., assignors to AMP Incorporated, Harrisburg,

Filed Nov. 29, 1968, Ser. No. 779,806 Int. Cl. H011- 13/54 US. Cl. 33975 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved actuating cam arrangement for a patchcord programming system.

An object of this invention is to provide a low cost cam arrangement for a programming system.

A further object is to provide such an arrangement which is simple to assemble and which provides a high degree of precision and reliability.

These and other objects will in part be understood from and in part pointed out in the following description.

A patchcord programming system is a multiple electrical contact assembly comprising a fixed rear bay and a removable frontboard. The rear bay has a number of fixed contact springs mounted for engagement respectively by the ends or tips of patchcords inserted into the frontboard. In use, a frontboard is inserted in the frame of the rear bay, being held generally parallel to the rear bay. Then the frontboard is cammed upward so that each of the patchcord tips in the frontboard presses with substantial force against a corresponding contact spring in the rear bay. To insure reliable electrical contact between each tip and spring, the frontboard is first cammed upward past its final rest position with respect to the rear bay, and then moved downward slightly. This gives a double or back wiping action of the contacting surfaces as they mate with each other.

Previously, the cams which were used with programming systems were costly assemblies of machined ec centric shafts with separate bearings fitted on them. The present invention provides a cam assembly in which the parts require substantially no machining, and fit together in self-indexing fashion to give a high degree of precision and reliability.

In accordance with the invention in one specific embodiment thereof the cams and bearing members in a programming system are made as integral moldings of a rigid self-lubricating plastic such as Delrin. These members are fitted on a square shaft in self-indexing fashion to achieve the necessary precision with a minimium of assembly time.

A better understanding of the invention together with a fuller appreciation of its many advantages will best be gained from the following description given in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a plugboard programming system embodying features of the invention;

FIG. 2 is an enlarged side view of the system; and

FIG. 3 is an enlarged exploded view of one of the cambearing members and related parts provided in accordance with the invention.

The patchcord programming system shown in FIGS. 1 and 2 comprises a rear bay 12, a removable frontboard Patented Nov. 10, 1970 14, and a cam arrangement generally indicated at 16. Inserted into various ones of the holes in the frontboard are a plurality of patchcords 18, whose tips mate with corresponding ones of the contact springs (not shown) carried by the rear bay. A more detailed description of such springs and the construction of a plugboard will be found in US. Pat. 3,324,443.

In the condition shown in FIGS. 1 and 2, frontboard 14 is in operating position and is being cammed upward (i.e. in a plane parallel to itself) relative to the rear bay by cam arrangement 16. To this end, there is provided a shaft 20 on the outer end of which is fixed an operating lever or handle 22, by means of which the unit can be opened or closed. The top of handle 22 is swung forward and down from the position shown to uncam the frontboard and permit it to be removed. Shaft 20, which is square, has fitted onto it a right cam member 24 and a left cam member 26. These members are mirror images of each other and are molded as finished parts in the configuration shown in FIG. 3. These members are suit ably made of Delrin 500 molding compound.

As seen best in FIG. 3, cam member 24 has a larger diameter portion 30 with an outer cam surface 32 which is cut away by a flat surface 34 and a fiat surface 36 to provide clearance of the cam with respect to certain other members in the assembled unit. This allows the unit and the cam members to be more compact. Integral with portion 30 of cam member 24 is a smaller diameter cylindrical portion 38 whose outer surface serves as a bearing. Extending axially through member 24 is a square hole 40, the walls of which mate closely with shaft 20. The center axis of hole 40 is coaxial with the outer surface of cylindrical portion 38 but is off center with respect to cam surface 32 of portion 30. As indicated in FIG. 3, cylindrical bearing portion 38 of member 24 extends through and provides a bearing against the inner surface of a thin-wall bushing 42 pressed through the side wall members of rear bay 12.

Positioned on the inner side of the wall of rear bay 12 is a bracket 43 having a notch 44 into which front board 14 fits. A similar bracket is positioned in the same way on the left side of the system. Bracket 43 has cut through it a hole 45 of a larger diameter than bearing portion 38. The bracket 43 is pivoted near its lower rear corner on a pin 46 which is riveted in the sidewall of rear bay 12. Because of the clearance provided between bracket hole 45 and bearing portion 38, each bracket is free to swing about 15 forward when the system is opened and a frontboard removed or inserted. Several spring washers 48 are inserted on portion 38 between bracket 43 and the sidewall of the rear bay to prevent handle 22 and bracket 43 from pivoting freely unless in operation.

The outer end of bearing portion 38 extends outward beyond the frame and is engaged by handle 22. Handle 22, cam member 24, and shaft 20 are fastened together by means of a roll pin 50. Left cam member 26, which is the mirror image of member 24, is fastened in place and serves as combined cam and bearing in the same way.

In an actual programming unit which has been built and successfully operated, shaft 20 was a one-quarter inch square steel rod, the length of cam member 24 was 1% inch, and its cylindrical portion 38 was 0.312 inch in diameter. The cam members withstood over a hundred pounds of force during closing for more than 50,000 cycles of operation. The shape of cam member 24 has been drawn substantially to scale in the drawings herein.

The above description is intended in illustration and not in limitation of the invention. Various minor changes in the embodiment shown may occur to those skilled in the art and may be made without departing from the spirit or scope of the invention as set forth.

What is claimed is:

1. In a programming system of the character described wherein a frontboard is to be inserted into and cammed generally parallel to a rear bay, an improved cam arrangement comprising a keyed shaft means, and a pair of cam members fixed on said shaft means, each member having a cylindrical bearing portion surrounding a respective outer end of said shaft means and an integral large diameter cam portion adapted to bear against an element of said system to cam the frontboard relative to the rear bay.

2. The arrangement in claim 1 wherein said cam members are of molded plastic such as Delrin and are minor images of each other, each member having an axial hole through it which mates with said shaft means.

3. The arrangement in claim 2 wherein said larger diameter portion of each cam member has an outer cam surface eccentrically located relative to the axis of said hole, said smaller diameter cylindrical portion being generally coaxial with said hole.

4. In a programming system of the character described, a rear bay adapted to receive a frontboard and having a frame including spaced apart side walls, said walls near the lower corners thereof having in-line, small diameter openings through them, a smallshaft having a polygonal cross section extending axially through said holes, a pair of molded plastic cam members each of which includes a larger diameter eccentric cam portion and a smaller diameter cylindrical bearingportion, each member having an axial hole concentric with said smaller diameter portion and which mates with said shaft, each member being fitted upon said shaft near a respective end thereof with the smaller diameter portion of the member extending through a respective hole in a side of said frame, said smaller diameter portion bearing against the wall of said hole in said frame, and handle means fitted upon an outer end of said shaft.

5. The assembly in claim 4 wherein the cam portion of each cam member includes an eccentric arcuate surface which is cut away along two surfaces to provide clearance in said assembly.

References Cited UNITED STATES PATENTS 9/ 1967 Brookman et a1. 12/1968 Campbell. 

